The present invention relates to thin-film deposition and etching processing employing focused beams of charged particles such as ions and electrons.
Focused ion beam processing where a hole of a prescribed shape is made in a sample surface and deposition is carried out by blowing source gas out from a gas gun while irradiating a focused ion beam, and which is achieved through sputter-etching or gas-assisted etching employing the kind of focused ion beam apparatus shown in FIG. 4 is widely implemented with respect to photomasks of semiconductor devices, etc.
In the drawings, numeral 1 indicates an ion source. Ions are extracted by applying a voltage to electrodes taken from this ion source 1 and these ions are brought into a beam-shape by an ion optical system 3, are deflected by a deflection operation of a deflector, and are made to irradiate desired locations of a sample 9.
Source gas is blown or injected from a gas gun 6 in the direction of the vicinity of the surface of the sample 9 to be subjected to deposition mounted on a sample stage 7 in the case of processing by deposition.
In doing so, the region of the sample 9 has an atmosphere of the blown source gas so that when a focused ion beam 2 is irradiated, ions and the source gas react with each other so that a certain product material, i.e. a volatile product material, is deposited on the surface of the sample.
When the focused ion beam 2 is made to scan a prescribed region of the sample 9 by the deflector, deposited matter forms a thin film at this region.
In the case of processing employing sputtering etching, when an ion beam is deflected by the deflector 4 in such a manner as to scan a specific region of the sample 9, ions collide with the surface of this region of the sample and material at the surface is detached so as to be scattered.
This process can therefore shave off specific locations. In gas-assisted etching where gases such as halogens are blown out from a gas gun 6 onto a region of the sample to be irradiated where an ion beam is irradiated, ions collide with the surface of the sample at specified regions of irradiation, displaced sample material reacts with an assist gas and is made volatile.
This process has the advantage of the processing speed being rapid at each stage compared with sputter etching that performs simple physical removal because the sample material actively eliminates volatility.
However, when a film-forming process is to be implemented on a certain pattern, when a region to be irradiated of the pattern is set and deposition is implemented, the thickness of portions at the periphery of the pattern becomes thin even if the ion beam acceleration voltage and bean current is kept constant and the number of scans is the same.
Further, when a process is to be performed where a hole is to be made in the pattern at the sample surface, a region of the pattern to be irradiated is set and patterning is performed, and even if the ion beam acceleration voltage and beam current is kept constant and the number of scans is the same, portions at the periphery of the pattern tend to be formed so as to be inclined in an obtuse manner.
Exactly the same can also be said for gas-assisted etching. The cause of this phenomena is that the focused ion beam, rather than being uniform in ion density, has the kind of normal ion distribution shown in FIG. 1A.
The scanning of a focused ion beam having this kind of normal distribution in one direction will now be considered.
After irradiating a certain point a for a fixed period of time, the focused ion beam is shifted in one direction by an interval corresponding to the diameter of the beam, and irradiation is executed for the same time. The beam is then shifted again in the same direction by an interval corresponding to the beam diameter, and irradiation is performed for the same period of time.
This operation is then sequentially repeated until a point b is reached.
The focused ion beam has an ion density distribution that has a normal distribution. This means that there is already some irradiation present even when the beam center is not present at a certain point, i.e. at the time when the beam center approaches in the next step or in a still further step.
The extent to which a certain point is therefore irradiated by an ion beam is therefore an estimated amount including when the center of the beam is not present at this point and when the beam is in the vicinity of this point.
This is shown in graphical form in FIG. 11. Here, a solid line shows the amount of ion irradiation when the beam center is at each point and a dashed line shows an estimated amount of ion irradiation after scanning.
The estimated amount of ion irradiation in the vicinity of the start point of scanning colliding with the end part of the pattern is low compared with that at the central part.
The same can also be said for the vicinity of each scanning end point and pattern end point.
This phenomena occurs not just for cases where ion beam irradiation scanning is performed in steps but also for sequential scanning in analog systems.
Further, the boundary is not limited to the scanning direction and also applies to boundaries between scanning lines, which gives rise to two-dimensional phenomena.
Eventually, this influence appears as blunting of the peripheral portions of the pattern in the previously mentioned deposition and etching processes.
When processing parts of large patterns, the ratio of parts at the boundary periphery is low and processing is therefore relatively uniform. However, for small patterns, the ratio of parts at the boundary periphery is high and processing therefore becomes insufficient.
This situation is shown in FIGS. 2A and 2B taking an example of deposition processing.
In FIG. 2A, there is shown a small pattern a, and a large pattern b.
A large portion of the small pattern is subjected to the influence of blunting at the peripheral portion of the pattern and is therefore constituted by a thinly applied region. However, with the large pattern, a thinly applied region subjected to blunting at the periphery of the pattern is small and is therefore constituted by a thickly applied region.
Cross-sections of each of the portions shown in I to IV of FIG. 2A are shown in FIG. 2B.
Here, cross-sectional thickness corresponds to the amount of irradiation with an ion beam.
As a result, with deposition and etching processing employing a focused ion beam apparatus of the related art, in order to process a pattern to a uniform thickness or a uniform depth, scanning time is changed for large patterns and small patterns.
This then results in an ineffective process where a scanning region is set for every pattern and individual processing is carried out even for ranges where beam scanning is possible.
In order to resolve the aforementioned problems, it is an object of the present invention to provide a processing method and device thereof capable of processing in a uniform manner so that deficiencies in the pattern boundary regions do not occur while at the same time enabling simultaneous processing of a plurality of patterns when performing deposition processing or etching processing on a prescribed pattern using a focused ion beam apparatus.
In the processing method of the present invention, there is implemented irradiation with a charged particle beam in such a manner that, when executing processing in a uniform manner, when deposition processing or etching processing of a prescribed pattern is carried out using a charged particle beam apparatus, a region of the pattern to be processed is divided up into microscopic regions having a size corresponding to the diameter of the beam, such that when the beam irradiates a respective microscopic region it also irradiates portions of adjacent microscopic regions, and regulation is performed by scanning circuits etc. with processing proceeding simultaneously for a plurality of patterns within the scanning region in such a manner that the dose amount for each microscopic region becomes equal.